The inventor of the present invention has strived to develop wave-power generation systems having high energy efficiency from when he worked at the Muroran Industry College of Japan. In detail, it pertains to using wave power having two kinds of complex motion mechanisms including vertical and horizontal motions. An oscillating plate is installed at a singular point at which interference between incident waves and reflected waves occurs, particularly, at a singular point at which vertical motion becomes zero while horizontal kinetic energy is doubled. Thereby, it is intended to provide a rational wave-power generation method, in particular, a pendulum wave-power generation method in which a generator using a hydraulic system can be efficiently operated.
In Japan, there are not many engineers who try to actively understand and use wave interference which is one of the fundamental notions of physics and has been disclosed in Patent document 1. Thus, there are very few people who recognize the achievements of the research of the inventor of the present invention. With regard to this, on the open sea, the energy efficiency of a practical apparatus using the high efficiency wave-power generation method was about 42% which is the world's highest.
The first practical apparatus to be manufactured by the inventor of the present invention as a hydraulic pump device for converting oscillating motion of the pendulum plate into rotary motion of a generator was a system using a large hydraulic cylinder. However, when the hydraulic cylinder is used, the power of impacting waves is applied to the pendulum plate and may cause fatigue failure of a cylinder mounting member or hinge pin. Further, in severe conditions of the open sea, a lubricant unit may malfunction. Therefore, to avoid the above problems, a simple power conversion mechanism which can withstand the severe natural conditions and has no dispensable member is required. A solution for this is to provide an oscillating vane type pump actuator which is integrally provided on an oscillating shaft of the pendulum plate and to limit the members which must maintain lubricating performance in the midst of severe natural conditions to a pair of bearings which support the oscillating shaft of the pendulum plate. In the case of the bearings, it is easy to maintain the lubricant performance. Mounting members integrated with the bearings are also strong. Thus, most of the problems can be solved. However, because the pressure resistance of oscillating vane pumps which have been commercialized is typically low, it is necessary to increase the pressure resistance two or three fold. The inventor of the present invention has also striven to solve such problems and has proposed a detailed technique of Patent document 2 which can be used even in pressure of 25 Mpa. As a result, the inventor of the present invention realized the development of a hydraulic high power conversion apparatus which is compact and has superior durability even in severe sea conditions. Moreover, based on such achievements, it has become increasingly possible for a large oscillating vane type pump actuator having specifications for high-pressure to also be used in a wave-power generation method using motion of a floating body, which has recently been attracting attention.
Typically, conventional hydraulic systems have simple valve structures which can control high power but consume a lot of energy. Recently, the age of technological innovation which highly evaluates energy saving technology has come about, so the hydraulic systems have changed into an electric-powered structure, and there has been a reduction in the market for hydraulic systems. Here, an advancement into new fields which has not been achieved by the conventional technology will be one of the best ways to counteract the shrinking of the market. A representative example of this is an oscillating actuator which can be used in a hinge unit of a large robot arm. For example, this can be used in a high-rise work for construction of a large windmill which uses natural energy. In the construction work of the large windmill, it is difficult to use an electric-powered structure, because the output of an electric motor is typically not sufficient.
As another field in which it is expected to be able to use the high-pressure oscillating vane actuator, the actuator may be used as an oscillating actuator for a steering device of a large ship. However, the oscillating vane actuator which is available on the market is a low pressure/small capacity actuator of 14 Mpa or less and cannot meet requirements of the shipbuilding or shipping industry which pursue minimization of space required to install the actuator.